Radhika Gupta (TIFR)  will be speaking in our Topology Seminar on 4th
November, 2022 at 4:30 PM in Ramanujan Hall.


Title: Stretch factors of graph maps and polynomial invariants of
free-by-cyclic groups

Abstract: In this talk we will associate two numbers, the geometric and
homological stretch factors, to a graph map and see under what conditions
they are equal. We will then upgrade these notions to free group
automorphisms. Finally, we will cast these numbers in terms of two
polynomial invariants, the Alexander polynomial and McMullen polynomial,
associated to a free-by-cyclic group and see how these polynomials are
related to each other.

Virtual Commutative algebra seminars

Speaker: Vivek Sadhu, IISER Bhopal
Date/Time: 4 November 2022, 5:30pm

Gmeet link: meet.google.com/sfo-vekm-yxz [1]

Title: Injectivity of Brauer groups for valuation rings
Abstract:  In the nonnoetherian situation, valuation rings often behave 
like regular rings. We will discuss several such results which are 
classically known to be true for regular rings, but also true for 
valuation rings. We then focus on Brauer groups. It is well known that 
Br(R) injects into Br(K) provided R is a regular domain and K=qt(R). We 
observe that the same is true for valuation rings. In fact, we will 
discuss a more general result in the setting of e'tale cohomology.

For more information and links to lecture notes and videos of previous 
seminars,

visit the website of VCAS:

  https://sites.google.com/view/virtual-comm-algebra-seminar [2]



Links:
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[1] http://meet.google.com/sfo-vekm-yxz
[2] https://sites.google.com/view/virtual-comm-algebra-seminar